Loading docks are frequently equipped with dock levelers that act to bridge the gap and height difference between the dock and the bed of the truck to enable material handling equipment, such as a fork lift truck, to move between the dock and the truck bed. One common form of dock leveler is what is referred to as an "edge-of-dock" type. With this type of dock leveler, no pit or recess is required in the loading dock and the dock leveler is mounted on the front vertical face of the dock.
A typical edge-of-dock dock leveler as disclosed in U.S. Pat. No. 3,685,077 is composed of a deck plate and an extension lip. The rear edge of the deck plate is hinged to the dock, while the lip is pivoted to the forward edge of the deck plate. In the storage position, the dock leveler is located in a generally horizontal position, while the lip assumes a pendant position in which it hangs downwardly in front of the dock.
As disclosed in the aforementioned patent, when it is desired to move the dock leveler to the operating position, the deck plate is manually pivoted upwardly to a generally vertical position, and a latch pivotally attached to the underside of the lip engages a rod or abutment on the dock leveler frame to lock the deck plate in the upper vertical position. In this upper position, the lip is located at an acute angle with respect to the deck plate and the upper edge of the lip is located above dock level. The deck plate is then manually forced outwardly away from the dock and the linkage between the deck plate and the lip and the supporting frame enables the outer edge of the lip to inscribe a generally curved path and move into engagement with the bed of a carrier or truck. In moving in this curved path, the outer edge of the lip initially moves upwardly, thereby ensuring that the lip will clear the bed of the truck, and then downwardly into engagement with the truck bed.
In use of the edge-of-dock dock leveler, as described in U.S. Pat. No. 3,685,077, the deck plate is pivoted to the vertical position manually by an operator standing on the dock and using a long bar or implement which engages the deck plate and pivots it to the vertical position. After the latch is engaged, the deck plate and lip are manually pushed forwardly to bring the lip into engagement with the truck bed. As the deck plate and lip have a substantial weight it is difficult to pivot the deck plate to the vertical position and then push the deck plate and lip forwardly. Therefore, there has been a need for an inexpensive, power operated mechanism to pivot the deck plate upwardly to its vertical position and then move the lip forwardly to its extended position on the truck bed.